Preserving Gulf Sturgeon—A Fish Tale of Gargantuan Proportions

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It's hard to imagine a better job than doing fieldwork with the USGS Coastal Ecology crew as they work to keep tabs on the Gulf sturgeon population.

Researchers lift a heavy sturgeon aboard the boat onto the scale

Researchers lift a heavy sturgeon aboard the boat onto the scale

The weather is beautiful, sunny and warm, perfect for a day outdoors and on the water. It's hard to imagine a better job than doing fieldwork with the USGS Coastal Ecology crew working to keep tabs on the Gulf sturgeon population. Almost every day in Florida is a great day to be out on the river, but it's especially nice when it's a workday and you have the water practically to yourself. 

Things start slowly, almost lazily, as the USGS Nekton plugs along, heading for a very specific location on the Suwannee River. "During the summer," explains Mike Randall with the USGS Coastal Ecology and Conservation program, "[Adult Gulf sturgeon] congregate in stretches known as 'holding areas;´we target these areas to maximize return on effort."

As the Nekton makes her way to one of these holding areas, the crew sorts through gear and nets, preparing for the work to come, laughingly asking who pays them to be out here, doing this. Soon though, the languorous atmosphere will be broken, replaced by hard, heavy work and a fast pace.

When the boat arrives at its destination, the crew prepares a large net, 300 feet long, 16 feet deep, and with 6-inch-wide mesh. The boat peels out, making a semicircle, setting the net, and then letting it drift downriver through the water. They release it with a 15-foot float, and then pause to enjoy the moment. This is Randall's favorite part: "When you've just set the net and everything thing looks beautiful and peaceful—before the chaos starts, before it's full of fish." 

Net deployed to catch Gulf sturgeon

Net deployed to catch Gulf sturgeon

In just a couple of minutes, the net floats start to bounce wildly, big sections of the floats are pulled underwater and upriver, and the crewmembers know they've caught some—that's when the adrenaline kicks in.

Gulf sturgeon are truly gargantuan fish, growing up to 8 feet long and weighing up to 200 pounds. The fish is dramatic to behold. With a long pointed nose and five rows of bony plates that run down their back and sides, sturgeon certainly look the part of a species that dates back to the age of dinosaurs. According to Randall, people tend to either love them or hate them on sight. Gulf sturgeon are endemic to the Gulf of Mexico and can be found in a series of rivers from the Suwannee River in Florida to the Pearl River in Louisiana. Like salmon, they swim back up river to spawn. Unlike salmon, they are bottom dwellers and are unable to climb fish ladders. Dams, weirs, reduced water flow, pollution, poaching, and other forms of habitat loss all threaten the survival of this ancient species.

The crew must work quickly to get the nets in and untangle the sturgeon from the twisted netting. As they untangle a fish, the crew ties a rope around its tail and throws it back in the water. Once the fish is tied to the boat and breathing, they know it is okay and they move on to the next, racing to get all of their catch roped, tied, and safely back into the water. When the haul is too large, some of the fish are cut loose from the netting, free to leave untagged, un-weighed, and unmeasured. 

Once all of the fish are out of the nets, the tension eases a bit, but not the pace. One at a time, they haul the sturgeon on board, where they have a limited window of time to "work it up."

Tagging a Gulf sturgeon

Tagging a Gulf sturgeon

The USGS Nekton is a 24-foot mullet skiff commonly known as a "birddog" for its propensity to point into the wind. The back end has a large flat area, where the fish are pulled in. If a sturgeon has been previously tagged, the tags are scanned; if not, three tags (a Floy t-bar tag for each pectoral fin and a PIT tag for the front of the dorsal fin) are inserted and scanned; and the fish is logged into the system. 

Next, they scoop the fish up onto a long flat board, and with the care of a patient being lifted into an ambulance, the fish is hoisted onto a large scale. From there, they slide the fish nose first into a large piece of PVC pipe that has been cut in half and fitted with handles and a ruler. The sturgeon slides down the pipe until it hits the end, and its length, from nose tip to tail, is noted and recorded. Finally, two crewmembers lift the fish and chuck it into the air over the water. The sturgeon hits the surface with a loud smack and an enviable splash. 

"Must they be so rough?" an outsider might wonder. As Randall explains, it's actually for the fish's sake that it is tossed into the air rather than slid gently back into the river. While outside the water, the sturgeon's swim bladder—the organ that allows the fish to move up, down, or remain at a level of buoyancy in the water—fills with air; if they gently slide the fish back into the river, the researchers find themselves watching with dismay as the fish floats down the river, belly up like an inflated balloon. With enough impact, however, the wind is unceremoniously knocked out of the creature, allowing it to return to the water with its buoyancy regulator under control. 

Once the sturgeon have all been worked up, the group lets out a collective sigh. In a trip on the Suwannee last year, they went through 1,820 pounds of fish in one outing. As Randall says, "That's a heck of a fishing trip." 

It is precisely this vulnerability to fishing during the summer spawning season that keeps Randall and his colleagues checking on these sturgeon from time to time, even though their numbers have climbed in recent years.

The Coastal Ecology group (then part of the U.S. Fish and Wildlife Service) started tagging Gulf sturgeon in 1986. The effort started as a preemptive strike; assuming the trajectory of fish would go down, they captured some and learned how to spawn and rear them. However, with commercial sturgeon fishing stopped in 1984, the number of sturgeon started to climb dramatically, and the hatchery efforts stopped.

The U.S. Fish and Wildlife Service listed the Gulf sturgeon as threatened in 1991. By 2001, the numbers on the Suwannee River were up enough that researchers felt comfortable reducing the frequency of their tagging efforts in this location. In their outing to the Suwannee last year, the 300-foot net was full in about two minutes. Thirteen fish were cut loose; 12 were measured and tagged; and none of the total of 25 captured had been tagged before. In terms of population growth, that's most likely a great sign. In 2001, roughly 30 percent of the fish they brought in were recaptures. A catch with no recaptured fish can only mean two things: either they are losing their tags or there a lot of new fish in the river.

Gulf sturgeon being weighed and measured

Gulf sturgeon being weighed and measured

While the Suwannee population of sturgeon has been stable or increasing for 20 years, there are still reasons for concern. The populations in most rivers are not nearly as strong as the Suwannee population. In the Pascagoula, for example, pulling in 25 fish over an entire year would be cause for excitement. Not only do the sturgeon´s spawning habits make large numbers of fish susceptible to easy capture at a time that's critical to the species' survival, the long generational lifespan of sturgeon—8 to 12 years for a male to mature and 12 to 16 for a female—means that it takes time to recover from population setbacks.

In 2001, the U.S. Fish and Wildlife Service needed numbers on the population in the Yellow River, and recently, that's where most of the crew's sturgeon efforts have been focused. Like most cases of threatened or endangered species, there's a balancing act between the needs of the animal and the needs of the human population. USGS studies of the sturgeon help decision makers such as the U.S. Fish and Wildlife Service, the National Marine Fisheries Service, and the National Oceanic and Atmospheric Administration understand the population size, critical habitat, life history, and other factors needed to preserve the Gulf sturgeon as a species.